Blast gun



Feb. 13, 1945. l.. KEEFER BLAST GUN Filed Dem.` 20, 1943 @m Wm. WQQQ QM mi N'NNH mmm www. QN

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' mn, waa-w -bg/aa Pnenfed Feb. 13, 194s BLAST GUN Walter L. Keefer, Hagerstown, Md.. assignor to Pangborn Corporation, Hagerstown. Md., a corporation of Maryland Application December 20, 1943, Serial No. 514,990

2 Claims. (Cl. 51-11) t The present invention relates to blast guns wherein abrading material is entrained by a propelling medium within the gun to be moved forwardly as a forcible blast stream. The invention more speciiically pertains to that type of blast gun providing a 'partial vacuum therein for drawing abrading material from a supply source to a position within the gun whereby the propelling medium moves the abrasive forwardly to provide a high velocity blast stream.

A conventional type of blast gun employed in the past embodying the injector principle includes a nozzle at the forward end of the gun and a smaller jet positioned rearwardly of the forward nozzle and in axial alignment with the bore of the larger forward nozzle. A partial vacuum is generated by such a device between the two nozzles for drawing abrading material into the gun for engagement with the propelling medium whereby the abrading material is moved forwardly and projected onto the article or surface to be blasted. In such a type of gun the propelling medium passing through the rear nozzle and issuing therefrom as a Jet expands within the larger nozzle for the creation of a partial vacuum and it appears that a material portion of the abrasive is pushed along the inner wall of the discharge nozzle. The engagement of the abrasive with the inner surface of the forward discharge nozzle causes wear therealong and the friction developed during such engagement provides a loss in the velocity of the blast stream passing through the forward discharge nozzle.

It is accordingly an object of the present invention to remove the disadvantages of such prior type of blasting device and to provide a lblast gun wherein the abradant is drawn into and inside an annular jet formed by the propelling medium moving forwardly at a high velocity so that the propelling medium is thus arranged on the outside of the abrasive as it is acceleratedl within the discharge nozzle to thereby provide a sheath of the propelling medium around the abrasive to reduce the wear on the discharge nozzle and to provide a concentration of the abrasive within the blast stream.

Another object of the invention resides in providing a rugged blast gun wherein the propelling medium is supplied around the abrasive material through an annular opening into a discharge nozzle of the gun including a replaceable forward discharge nozzlewhich may be mounted on the gun without disturbing the anlses nular opening through* which the propelling medium is supplied.

A further object of the invention pertains to the provision of a blast gun that may be economically manufactured and readily assembled with the parts thereofreplaceable and particularly the discharge nozzle by an operator who lacks skill and acquaintance with the art of electors or the science dealing with the creation of a partial vacuum by changes in velocity and pressure so that the gun will function efficiently in the field even though the discharge nozzle parts are replaced by a layman.

Other objects and features of the invention will be more apparent to those skilled in the art upon a consideration of the accompanying drawing and the following detailed description wherein an exemplary embodiment of the invention is disclosed.

In the drawing:

Fig. 1 is a side elevational view of a blast gun embodying the invention.

Fig. 2 is an axial sectional view of the blast gun shown in Fig. 1.

Fig. 3 is a side elevational view of the discharge nozzle member.

In carrying out the invention the blast gun is designed for the purpose of entraining abrasive material of any granular type so that such abrasive will be moved forwardly at high velocity for impingement upon an article to be abraded or a surface to be blasted or for knocking out sand cores of castings. A gun embodying the invention is adapted to generate or create a partial vacuum within the gun barrel so as to draw or suck the abrasive material from a supply into the gun where the abrasive is entrained by the propelling medium which creates the partial vacuum so that the abrasive is moved forward at a high velocity from the forward end of the gun in the form of a forcible blast stream.

Referring to the drawing there is shown at II a gun body preferably formed or cast in one piece and provided with passages therein for 6the propelling medium and the abrasive material.

The body I I may be provided with handles I2 and I4 for the purpose of manually manipulating the gun particularly when ,the propelling medium is a liquid such as water under pressure of four hundred pounds per square inch and greater. The handles I2 and- I4 may be formed integral with the gun body II and they are preferably hollow for the purpose of reducing the weight of the gun assembly. 1n normal operation the 69 handles I2 and Il are usually arranged in a substantially vertical plane so that the handle Il extends upwardly/4 In carrying out an abrading or blasting operation wherein liquid forms the propelling medium some of the splattered fluid may fill the handle I4 and a drain opening il may therefore be provided in the handle adjacent the gun body for the purpose of permitting the escape of the liquid from within the handle Il.

The gun body .Il vterminates at the forward end thereof in an annular portion Il having threads Il on the outer surface forl receiving a retaining jacket for the discharge nozzle as hereinafter described. The annular end portion Il thus -provides anopening in the forward end of the gun body substantially concentric of a passage in the gun through which the abrasive assasve ll velocity and pressure without altering the operating characteristics of the gun. It is for this purpose that the forward discharge nozzle is made in two parts so that the more rapidly wearing Part may beA readily replaced without 15 disturbing the part which provides a precisely is supplied. 'I'he gun body immediately rearwardly of the annular end portion Il is provided with a cavity or chamber 22 of any suitable cross sectional shape and in the embodiment illustrated is'formed with arcuate walls for the purpose of reducing thesize of the chamber and at the same time providing' a chamber of adequate dimensions for receiving a quantity olf the propelling medium. 'Ifhe normally lower portion of the gun body il is provided with a passage dimensioned annular opening around the foriward end of the nozzle member 32. Thus the forward discharge nozzle may`comprise a replaceable nozzle member 43 and a sleeve Il "20 which need not be replaced as often as the member 43.- 'Ihe sleeve 48 may be mounted within the opening in the annular end portion it ofthe gun body Il in any suitable manner and in the embodiment illustrated the sleeve I3 is formed 25 with an external dimension so as to fit tight in or conduit N through which the propelling medium is supplied to the chamber 22. The rear end portion of thepassage 24 may be threaded as indicated at 2t for receiving apipe tube such as a rubber hose 29 supplying the propelling medium under pressure to the gun and vinto the passage 24 which communicates with the chamber 22.

The gun body il is also provided with an axial opening or passage 3l rearwardly of the chamber 22. A replaceable nozzle member 32 may be securely mounted within the gun body in any suitable manner and in the structural arrangement illustrated the nozzle member 32 is of such the opening in the annular end portion it. The rear end portion od the sleeve 4l is preferably formed as a substantially cylindrical bore so as to surround the forward end of the nozzle mem- 30 ber 32 in a spaced relation and provide an anconnection 2l. 'Ihe outer end portion of the pipe connection 2B is adapted to receive a nexible nular opening I2 therebetween. The forward end of the sleeve Il is provided with an annular flange 54 which abut's against an annular shoulder provided in the end portion I8 of the 15 gun body so as to limit the rearward movement of the sleeve I3 in the mounting thereof in the gun body Il. The forward end of the sleeve Il! is provided with a conical surface indicated at il for the purpose of providing a seating surface u for the rear end of the nozzle member It.

external dimensions as to fit tightly within the The discharge nozzle member 43 is preferably formed with a substantially cylindrical outer surface for fitting snugly within a retaining Jacket 3l. The rear end ofthe nozzle member 48 is pron vided with a conical surface 62 corresponding is reduced such as by a grinding operation so as to provide a'substantially cylindrical outer end substantially to the taper of the conical surface $3 formed in the end of the sleeve I3. The retaining jacket 58 is provided with an inturned flange 64 at the forward end so that the conical so end 62 of the nozzle member i6 will be urged into seated engagement with the conical surface 53 of the sleeve 8 when the retaining jacket is threaded on the threads I1 of the annular portion I8 of the gun body. The jacket member 5G is g5 provided with an enlarged internally threaded outwardly in proceeding towards the rear end The nozzle member 32 terminates at l skirt tl having flat portions $3 thereon for Inanipulation by a conventional wrench. A resilient washer 83 may be interposed between the flange 84 and the forward end of the nozzle 59 member 46. Thus the conical surfaces 56 and @2 nozzle member 32 when this nozzle is mounted `f in the opening 3| in the gun body.

vthe nozzle member 32 and in the structure shown on 'the drawing the gun body it adjacent the cooperate to properly align the bore of the nozzle member I3 with that of the sleeve 48.

The area of the annular opening 52 provided around the forward end of the nozzle member so 32 is of importance in the functioning of the gun rear portiontof the nozzle member- 32 is provided with a lpipe tting 42 suitably threaded in the un bod Ii so as to rovide open comg y p opening around the forward end of the nozzle munication with the boreof the nozzlemember 32. In this connection it is to be noted that the opening in the gun body for the pipe fitting 42 is sumciently large to introduce the nozzle member 32 therethrough and to remove this nozzle member when replacement thereof is necessary. A flexible tube such as a rubber hose u extendso as to produce a pronounced partial vacuum in the space immediately in front o! the nozzle member 32. The dimensions of the annular Vim may 'be adjusted at the factory and are not susi ceptible of variation during replacement of the 1l altering the annular opening B2 between the in ner surface of the sleeve 46 and the forward pe ripheral end of the nozzle member 32. The nomle member 32 and the sleeve 48 may require replacement at less frequent intervals. These parts may be readily mounted in the gun body by a maintenance employee without altering the operating characteristics since the flange 36 xes the position of the nozzle member 32 and the ange 64 xes the position of the sleeve 4B so that the factory adjusted dimensions of the annular opening 62 are restored.

The bore of the discharge nozzle member 46 is preferably larger at the rear end thereof than at the forward end to provide an inwardly oonverging surface in proceeding forwardlythrough the nozzle. In the specific structure depicted in the drawing the rear end portion of the bore in the discharge nozzle 46 is conical shaped and merges with a similar shaped bore in the sleeve 48. Thus the propelling medium escaping from the chamber 22 through the annular opening 62 provides a conical jet hollow at the center thereof forwardly of the nozzlel member 32 to create a pronounced vacuum in this space. The vacnum thus generated draws the abrasive material from the hose Minto the hollow cone formed by the propelling medium where the abrasive is entrained and moved forwardly through the bore of the discharge nozzle. The propelling medium thus forms a sheath around the abrasive to prevent engagement of the abrasive particles with the inner wall of the sleeve 48 and the inner wall of the nozzle member 46 and thereby reduces the wear on this discharge nozzle assembly. As the composite blast stream moves forwardly the converging walls of the nozzle member 46 reduce the area of the hollow center to facilitate the entrainment of the abrasive particles by the propelling medium and to concentrate the abrasive in the center of the blast stream. The outer end portion of the bore in the nozzle member 46 may be cylindrical shaped as shown at 60.

The gun herein shown' and described is designed primarily for use in hydroblasting wherein wet sand or a slurry of sand and water forms the abrasive material and wateris employed as the propelling medium. The gun functions equally well when other abrasive material such as steel shot. grit and the like are employed and compressed air serves as the propelling medium.

I claim: v

1. In a blast gun, an elongated= gun body having an opening in the forward end thereof and a cavity rearwardly of said opening and a passageway extending rearwardly from the cavity,

a removable sleeve mounted in the opening at the forward end of the gun body, a flange carried by said sleeve engaging the'forward end portion of the gun body, a nozzle member mounted in said passageway extending through said cavity into the rear end of the sleeve to provide an annular opening between the inner surface of the sleeve and the exterior surface of the nozzle member, a flange carried by the nozzle member engaging the gun body 'limiting the forward movement of the nozzle member, means for supplying a propelling medium under pressure to said cavity and around said nozzle member through said annular opening to provide a partial vacuum in said sleeve for drawing abrasive through said nozzle member, a discharge nozzle having a bore extending therethrough, a conical surface formed within the forward end of said sleeve, a conical surface on the rear end of said discharge nozzle, and removable means maintaining the discharge nozzle in substantially axial alignment with the axis of the sleeve and the conical surface thereon in seating engagement with theconical surface Within said sleeve.

2. In a blast gun, an elongated gun body having an opening in the forward end thereof and a cavity rearwardly of said opening and a passageway extending rearwardly from the cavity, a removable sleeve mounted in the opening at lthe forward end of the gun body; a flange carried by said sleeve engaging the forward end portion of the gun body limiting rearward movement of the sleeve, a nozzle member mounted in said passageway and extending through said cavity into the rear end of the sleeve to provide an annular opening between the inner surface of the sleeve and the exterior surface of the nozzlemember, a flange carried by the nozzle member limiting the forward movement of the nozzle member, said gun body having a passage therein for supplying a propelling medium under pressure to said cavity and around said nozzle member through said annular opening to provide a partial vacuum in said sleeve for drawing abrasive through said nozzle member, a discharge nozzle having a bore extending therethrough, an outwardly ared conical surface in the forward end of said sleeve,

said gun body retaining the conical surface of e said discharge nozzle in seated engagement with the conical surface in said sleeve.

WALTER L. 

